The CMB Infectious Disease Pathogenesis Section assisted Principal Investigators with experimental design, tissue collection and preparation, interpretation of histopathology findings, and assistance with manuscript preparation. CMB Research Support Specialists also provided technical expertise and support to NIAID Principal Investigators, assisting them with true cage to benchside support. Both pathology and technical proficiency resulted in numerous co-authorship opportunities. The CMB has successfully maintained a gnotobiotic facility, which consists of 12 bio-exclusion units designed to keep the mice from becoming colonized with any adventitious microorganisms. Germ-free mice are free of all aerobic and anaerobic organisms with the possible exception of endogenous viruses. Breeding colonies and mice on study are maintained in semi-rigid isolators provided with HEPA-filtered air and autoclaved food, bedding, and supplies. Strict SOPs are followed to maintain the mice in a germ-free state. The CMB has an active Assisted Reproduction Technologies and Cryopreservation unit. A mission of the Comparative Medicine Branch (CMB) is to provide support to the emerging and re-emerging infectious disease research conducted within the NIAID/DIR Animal Biosafety Level (ABSL) 3 facilities.